Small worms of Sthenelanellinae, Pholoinae and Pisioninae (Annelida, Sigalionidae) from the Tropical Northwestern Atlantic

The family Sigalionidae is characterized, among other features, by including scale worms with large bodies. However, among sigalionids, the subfamilies Sthenelanellinae, Pholoinae, and Pisioninae stand out by their small representatives with few segments and fragile bodies. In the Tropical Northwestern Atlantic, which includes part of the Gulf of Mexico and the Caribbean Sea, these subfamilies have been rarely studied, with few species recorded, and questionable records. This contribution aims to improve the knowledge of sthenelanellins, pholoins, and pisionins in the region through a faunistic study based on material from two Mexican scientific collections: the Reference Collection of Laboratorio de Biodiversidad y Cambio Climático (BIOMARCCA) and the Reference Collection of Benthos (ECOSUR) of El Colegio de la Frontera Sur. Pisione wolfi is confirmed from the Tropical Northwestern Atlantic, and three new species are described: Sthenelanella pechi sp. nov., S. sarae sp. nov. and Taylorpholoe anabelae sp. nov. A key to all Sthenelanella and Taylorpholoe species is also included.

The members of these three subfamilies are typically recognized as small fragile worms with heterogeneous morphology. In the Tropical Northwestern Atlantic, the study of sthenelanellins, pholoins, and pisionins has been scarce with few species recorded.

MATERIALS AND METHODS
The study area considers the Gulf of Mexico and the Caribbean Sea, two regions frequently referred together as the Grand Caribbean Region, covering from Bermuda to central Brazil (Salazar-Vallejo, 1996). However, since the area encompasses a wide range of geographic and oceanographic conditions that cannot be restricted to mention solely as Caribbean conditions; the revised classification of the marine regions and environments proposed by Spalding et al. (2007) was used in this contribution.
The examined material came from two Mexican scientific collections: the Reference Collection of Laboratorio de Biodiversidad y Cambio Climático (BIOMARCCA) and the Reference Collection of Benthos (ECOSUR) of El Colegio de la Frontera Sur. The specimens from BIOMARCCA were deposited in the ECOSUR collection, as it guarantees their safety and availability for further consultation. Benthic marine sigalionids were collected from several localities along the Tropical Northwestern Atlantic. Specimens were fixed using a 10% formalin-seawater solution and preserved in 70% ethanol. Examined specimens were temporally stained with Shirlastain-A to enhance morphological details, mainly prostomial and parapodial features. Once the specimens were stained, they were observed and photographed. For scaled sigalionids, elytra were dissected and cleaned immersed in a 1:1 white vinegar-ethanol solution. Elytra and palpal sheaths. Segment 1 might possess inner tentacular lobes (lamellae). Ctenidial pads present; lacking stylodes. Notopodia on median and posterior segments with large, specialized sacs that produce feltage chaetae used to reinforce tube. Notochaetae of two kinds, long verticillate or short geniculate. Neurochaetae spinigers with short, sickle-or rod-shaped blades, except on the first segments which are falcigers with articulate blades. Elytra might possess patterns of pigmentation (after Pettibone, 1969;Aungtonya & Eibye-Jacobsen, 2013;Tilic et al., 2021; Eibye-Jacobsen, Aungtonya & Gonzalez, 2022).  Thomassin, 1972 1A). Mid-dorsal line smooth, some elytra lost, venter smooth. Elytra on segments 2, 4, 5, 7, alternate segments to 25, then present in all segments. Elytrophores bulbous, short, slightly larger in posterior segments. Prostomium pale orange, oval, wider than long. Two pairs of eyes, anterior eyes larger, visible dorsally. Lateral antennae short, barely seen, dorsally fused with tentacular segment. Median antenna with short ceratophore, 1/3 as long as prostomial length; basally with two auricles semispherical with margins bent, small, 1/2 as large as median antenna ceratophore; style short, twice as long as ceratophore (Figs. 1B and 1C). Without dorsal tentacular crest. First segment uniramous, chaetae simple verticillate. Dorsal tentacular cirri long, three times longer than neuropodia, ventral cirri shorter than dorsal tentacular cirri. Palps long, reaching segment nine, without palp sheaths. (Fig. 1B). Pharynx everted with 24 distal lanceolate papillae (Figs. 1B, 1D and 1E), and two subdistal lateral papillae (Fig. 1B, arrow). Ctenidial pads from segment three, three pads: one placed below elytrophores, other inserted dorsolaterally above the notopodia, and other on the dorsal side of the notopodia. Branchiae from segment two, placed below the elytrophore or tubercles, conical, short, 1/2 as large as elytrophores, cilia not perceived.
Posterior region tapered, pygidium depressed, rounded, and glandular with two long anal cirri, as long as the last six segments, anus dorso-terminal (Fig. 1A, insert).
Distribution. Tropical Northwestern Atlantic: Southern Gulf of Mexico, only known from the type locality.
Etymology. The species is named after Daniel Pech (ECOSUR-Campeche) in recognition of his efforts in studying marine benthos in the Gulf of Mexico. Also, he kindly made available most of the material examined in this study. The epithet is a noun in the genitive case (ICZN, 1999, Art. 31.1.2). Remarks. The genus Sthenelanella has been recorded from warm temperate and tropical waters, mostly from the Indo-Pacific coasts. From the Western Pacific, S. japonica Imajima, 2003 agrees with S. pechi in some features, such as lacking a dorsal tentacular crest and having a papillate neuracicular lobe. However, S. japonica stands out among Sthenelanella in having inner palpal sheaths in the basis of the palps, whereas S. pechi sp. nov. lacks palpal sheaths. Another difference is the pigmentation pattern in the posterior elytra. Sthenelanella pechi sp. nov. has elytra with a mottled band pattern, occurring from the elytral insertion to the lateral margin of the elytra, where the pattern tends to be sparse, and the color gets lighter, whereas S. japonica has elytra with a mottled random pattern, with spots occurring near to the elytral insertion, and in the lateral and proximal margin of the elytra, with its color uniform. Another species that resembles to S. pechi sp. nov. is S. corallicola Thomassin, 1972 from Madagascar; both species possess the first elytra rounded and blades articulate in neurochaetae from anterior segments. However, S. pechi sp. nov. differs from S. carallicola in having ctenidial pads from segment two, elytra from posterior segments oblong with smooth margins, and a mottled band pattern. Whereas S. corallicola has ctenidial pads from segment three, elytra from posterior segments subreniform with submarginal papillae in lateral borders, and colorless. Another difference between these two species is the number of pharyngeal papillae. The holotype of S. pechi sp. nov. shows the pharynx completely everted with 12 paired papillae, 24 papillae in total, while S. corallicola shows about 14 paired papillae, 28 papillae in total (Thomassin, 1972: 256, figs. a, c). From the Southwestern Atlantic, only one species of Sthenelanella has been described: S. peterseni Lana, 1991. The newly described Sthenelanella pechi sp. nov. resembles S. peterseni in having posterior elytra with smooth entire margins, articulate blades in neurochaetae from anterior segments, and neuracicular lobe with papillae. However, S. pechi sp. nov. differs from S. peterseni in having larger auricles, 1/2 as long as the median antenna ceratophore, neurochaetae from anterior segments with entire blades, and branchiae from segment two. Whereas S. peterseni has small auricles, 1/4 as long as its median antenna ceratophore, neurochaetae from anterior segments with entire or bifid blades, and branchiae from segment five. Another species in the region that resembles S. pechi sp. nov. is S. sarae sp. nov., described below; however, obvious differences can be found in prostomial and elytral features. Sthenelanella pechi sp. nov. has small auricles, 1/2 as long as the median antenna ceratophore, first elytra rounded with smooth margins, with mottled semi band pattern occurring from the elytral insertion to the lateral margin, posterior elytra oblong with mottled band pattern. Whereas S. sarae sp. nov. has large auricles, as long as the median antenna ceratophore, first elytra rounded with several lateral papillae, with mottled "C" shaped pattern, surrounding the elytral insertion, posterior elytra rounded with a narrower mottled band pattern. Despite these two species are found in the same region, they are associated with different bathymetric distributions, S. pechi sp. nov. is distributed in shallow waters, less than 50 m deep, while S. sarae sp. nov. is found in deeper waters, between 76-148 m deep. Description of holotype (ECOSUR 295). Specimen incomplete with 21 segments, 1.2 cm long, 0.2 cm wide. Body translucent, damaged posteriorly, broad (Fig. 4A). Mid-dorsal line smooth, some elytra lost, venter smooth. Elytra on segments 2, 4, 5, 7, alternate segments to 25, then present in all segments. Elytrophores flatten, short, slightly larger in posterior segments.
Prostomium whitish, oval, wider than long. Two pairs of eyes, anterior eyes larger, all eyes visible dorsally. Lateral antennae short, barely seen, dorsally fused with tentacular segment. Median antenna with long ceratophore, as long as prostomial length; basally with two auricles ear-shaped with margins bent, large, as long as median antenna ceratophore; style short, twice as long as ceratophore (Fig. 4C). Without dorsal tentacular crest. First segment uniramous, chaetae simple verticillate. Dorsal tentacular cirri short, as long as neuropodia, ventral cirri shorter than dorsal tentacular cirri. Palps long, reaching segment 8, without palp sheaths (Fig. 4B). Pharynx partially everted, ECOSUR P3232 specimen with pharynx damaged, fully everted with distal 28 lanceolate papillae and two subdistal lateral papillae. Ctenidial pads from segment three, three pads: one placed below elytrophores, other inserted dorsolaterally above the notopodia, and other on the dorsal side of the notopodia. Branchiae from segment 2, placed below the elytrophore or tubercle, flat and tapered, short, 1/4 as large as elytrophores, cilia not perceived.
First right elytron small, rounded, fragile, with several short filiform marginal papillae (Figs. 3O, 4D and 4E). Second right elytron missing. Posterior right elytra larger, rounded, with smooth margins (Figs. 3P and 4F). Surface of all elytra partially colored with brown spots as mottled "C" shaped pattern in the first pair of elytra, in posterior elytra with mottled band pattern, all elytra with few small globular papillae (Fig. 4F).
Posterior region lost.
Distribution. Tropical Northwestern Atlantic: Floridian ecoregion, Southern Gulf of Mexico and Western Caribbean; from Florida, USA to Yucatan Peninsula, Mexico (Wolf, 1984).
Etymology. The species is named after Sara Balam, in recognition of her effort during many years as a technician assistant in the Laboratorio de Biodiversidad y Cambio Climático, ECOSUR-Campeche. The epithet is a noun in the genitive case (ICZN, 1999, Art. 31.1.2).
Remarks. In the Gulf of Mexico, the only record of the genus Sthenelanella was made by Wolf (1984) from Florida and Alabama. He described and illustrated Sthenelanella sp. A, characterized by having large auricles, as long as the median antenna ceratophore (Wolf, 1984: 25-22, fig. 25-20a), first elytra rounded with several lateral papillae and with a mottled "C" shaped pattern near to the elytral insertion (Wolf, 1984: 25-22, fig. 25-20b, c), and blades with bifurcate tips in neurochaetae from anterior segments (Wolf, 1984: 25-22, fig. 25-20k, m-p). These features seem to agree with those found in S. sarae sp. nov., thus, it is possible that Wolf's previous record refer to the newly described S. sarae sp. nov. The latter will be confirmed once Wolf's specimens are studied. Wolf (1984: 25-24) compared Sthenelanella sp. A with S. ehlersi (Horst, 1916) and S. corallicola, and stated some differences found in Sthenelanella sp. A, such as the bifid blades in neurochaetae from segments 2-5, the rounded and pigmented "C" shaped pattern in the first elytra pair, and the highly papillate neuropodial lobe in segment two. One additional difference is the large size of its auricles, being as long as the median antenna ceratophore, while in S. ehlersi and S. corallicola the auricles are short, both about 2/3 as long as the median antenna ceratophore (Thomassin, 1972: 256, figs. 1a, 1c;Pettibone, 1969: 435, fig. 1a).
Sthenelanella sarae sp. nov. also stands out by having neurochaetae with thick handles in posterior segments, the same width along the handle, including the joint with the blade. This kind of neurochaetae is also found in S. uniformis Moore, 1910, S. japonica and S. peterseni. However, S. sarae sp. nov. differs from S. uniformis in having posterior elytra rounded with a mottled transversal band, whereas S. uniformis has posterior elytra reniform with a large brown patch on the anterior elytral margins (Moore, 1910: Pl. 33, fig. 108;Pettibone, 1969: 432, fig. 2b). Regarding S. japonica and S. peterseni, S. sarae sp. nov. differs from both species in having particularly large auricles, as long as median antenna ceratophore, and posterior elytra with a mottled transversal band pattern, while both species possess small auricles, about 1/4 and 1/2 as large as median antenna ceratophore, respectively, and posterior elytra with an undefined mottled pattern or without pigmentation, respectively. On the other hand, S. sarae sp. nov. shares distribution in the Gulf of Mexico with another Sthenelanella species herein described, S. pechi sp. nov. Both species are easily differentiated based on the size of the auricles, the pigmentation pattern in the first elytra, and the shape and pigmentation pattern in the posterior elytra (see remarks section of S. pechi sp. nov.). Prostomium partially fused with the first segment, oval, wider than long. Two pairs of eyes, all of similar size, visible dorsally. Lateral antennae short, inserted on the anterior border of the prostomium in the cephalic peak. Median antenna inserted occipitally on prostomium, short, 1/4 as long as prostomium (Figs. 6B, 6C and 7B). First segment directed anteriorly, achaetous, dorsal, and ventral tentacular cirri short. Palps short thick, laterally displaced, reaching segment two (Figs. 6A and 6C).
Variation. Paratype and additional material with pharynx fully everted with 18 lanceolate distal papillae and two subdistal lateral papillae, eyes barely seen; prostomium folded, and eyes could be partially concealed by first segments. Males with large masses of sperm in middle segments. Etymology. The name of this species is a humble recognition of the great labor done by Anabel León as a technician assistant in the Laboratorio de Biodiversidad y Cambio Climático (BIOMARCCA), ECOSUR-Campeche for many years. The epithet is a noun in the genitive case (ICZN, 1999, Art. 31.1.2).
Remarks. Before this study, the genus Taylorpholoe Pettibone, 1992 was considered monotypic, with T. hirsuta (Rullier & Amoureux, 1979) as its only species. Taylorpholoe hirsuta appeared to have a wide distribution in the West Atlantic Ocean, from South Carolina, USA to Brazil (Pettibone, 1992); however, with T. anabelae sp. nov. taking place in the same region, the previous records of T. hirsuta should be carefully revised.
As both species belong to the genus Taylorpholoe the similarities between T. hirsuta and T. anabelae sp. nov. are noticeable; however, T. anabelae sp. nov. differs by having a notopodial stylode with a large wide basis and, elytra with consistently abundant fimbria, whereas T. hirsuta has short slender notopodial stylodes and elytra with sparse long fimbria. The main difference between both species is noted in the dorsal papillae. Taylorpholoe anabelae sp. nov. has larger and bulbous papillae, completely covering the dorsum, while T. hirsuta present small and flat papillae, only covering the middorsal line (Padovanni, 2014: 59, fig. 7). Pettibone (1992) recombined Pholoe minuta hirsuta and elevated its status, using it as the type species of Taylorpholoe. She used material from the Tropical Northwestern Atlantic and beyond, including the type material from central Brazil. The redescription also included the material previously examined by Taylor (1971) from Florida, which fits the original description, and the first elytra from the holotype. However, the elytra did not match Taylor's illustrations (1971: 115, figs. E-I), or drawings by San Martín, Aguirre & Baratech (1986: 13, fig. 5A), nor the illustrated for T. anabelae sp. nov. (Figs. 3V, 3W, 6E-6G and 7D). Type or topotype material of T. hirsuta should be used to properly complete the description of the species which will enable comparisons with congeneric species. Currently, the description of T. hirsuta made by Padovanni (2014) is the most comprehensive and well-illustrated description.
In addition, in the proposition of the genus Taylorpholoe, Pettibone (1992) recorded juveniles and adults of T. hirsuta; she recognized the smallest specimens with 11 segments as juveniles, and those with 14-19 segments and signs of oocytes or juveniles beneath elytra as adults. Padovanni (2014) revised 124 specimens with a range of 14-16 segments, and despite she did not specify if the specimens possessed oocytes or juveniles, it is possible that her specimens were adults. Here, the specimens examined had 13-15 segments, and all presented either sperm (ECOSUR 297), oocytes, or juveniles (ECOSUR 296; ECOSUR P3233). Ehlers, 1901Pisione Grube, 1857Pisione Grube, 1857 Type species. Pisione oerstedii Grube, 1857 by monotype.
Copulatory parapodia and organs not seen. Posterior region lost.
Distribution. Tropical Northwestern Atlantic: Western Caribbean, Greater Antilles, and Southern Caribbean, from Quintana Roo, Mexico to National Park Archipelago Los Roques, Venezuela.
Remarks. These specimens match the original description by San Martín, López & Núñez (1999); however, some subtle differences were detected. The specimens here examined show the cerebral ganglion slightly displaced posteriorly, covering from the mid-section of segment five to the posterior margin of the buccal segment, without touching the buccal acicula and the jaws were located between the segments five and six. On the other hand, San Martín, López & Núñez (1999: 32, fig. 1A) described that in their specimens the extension of the cerebral ganglion comprehended from the posterior section of the segment four to the peristomium, reaching the basis of the buccal acicula, and the jaws were described and illustrated at segment five. The number of chaetae per segment (except segment one) also varied. Here, the examined specimens have 6-7 chaetae per segment (one superior simple chaetae, one spiniger, three lower falcigers and two lowest falcigers), while P. wolfi was described with five chaetae per segment (one superior simple chaetae, one spiniger, and three lower falcigers) (San Martín, López & Núñez, 1999), the same number of chaetae in the P. wolfi recorded by Díaz Díaz, Bone & López-Ordaz (2015) from National Park Archipelago Los Roques, Venezuela. Pisione wolfi was described using mature male specimens, whereas here the examined specimens are incomplete and possibly immature, as deduced by the lack of copulatory organs or gametes.

DISCUSSION
This study increases the knowledge of the sigalionid diversity of the Tropical Northwestern Atlantic with the confirmation of the record of Pisione wolfi in the region, and the description of three new species. The new species fit within the genera Sthenelanella (S. pechi sp. nov. and S. sarae sp. nov.) and Taylorpholoe (T. anabelae sp. nov.).
Since the erection of Sthenelanella over 100 years ago, only six species have been described; back then, using features in the body, parapodia, and elytra. Subsequent redescriptions, such as the ones made by Pettibone (1969), have broaden the descriptions of the species by evaluating in detail the prostomial features, first anterior segments, elytral features and the diverse kind of chaetae. This initiative for more detailed descriptions was also followed by Thomassin (1972), Lana (1991), Imajima (2003), Wehe (2007) and Aungtonya & Eibye-Jacobsen (2013). Here, the descriptions of the new Sthenelanella species have attempted to cover the classical features as well as the attributes included in recent studies, to make the descriptions comparable among the known species of the genus.
Some of the most contrasting attributes among Sthenelanella species are found in the elytra, such as their shape and pigmentation pattern. The specimens of the two new species of Sthenelanella agree with two of the three kinds of pigmentation patterns recognized by Imajima (2003): transversally banded (S. pechi sp. nov. and S. sarae sp. nov.) and pigmentation mottled (S. sarae sp. nov.). Further, it should be noted that the site where the pigmentation occurs and its coverage are also diagnostic and discriminant among species.
Regarding notochaetae, recently Tilic et al. (2021) explored the so-called thread-like fibers, hairy or feltage notochaetae of Sthenelanella by studying the process of chaetogenesis and ultrastructure of the chaetae, concluding that these are fibrous feltage chaetae, that emerge from modified chaetal sacs. Several authors have stated that the bundles of feltage chaetae appear in the middle segments, usually between segments 14-16 (Hartman, 1939;Fauvel, 1958;Lana, 1991;Imajima, 2003;Tilic et al., 2021). Here, the same segments were dissected and described from specimens of S. pechi sp. nov. and S. sarae sp. nov.; unfortunately, the chaetal sacs went missing during mounting on the slides, but were observed while dissecting the segments. All the Sthenelanella specimens examined herein had only a few short feltage chaetae, and none was collected with a fibrose tube. It is important to note that the specimens were collected from sediment by nucleator sampling from the sea bottom, which could result in chaetae being lost during the sampling; or perhaps, the interstitial habitat where the specimens were found led to the loss of long chaetae that might prevent free displacement among sand grains.
Regarding the neurochaetae, the chaetal unit classification proposed by Cruz-Gómez (2022) for pelogenins has been also proven useful for the genera Sthenelanella and Taylorpholoe, especially for descriptions and comparisons.
Unlike parapodia of pelogenins, sthenelanellins and pholoins have lesser complex parapodia, which is reflected in the distribution of the neurochaetae in the neuropodia. However, some similarities and differences regarding the neurochaetae distribution pattern were noted among the subfamilies, based on the species here examined. The similarities among the species evaluated are in the site of insertion of the units. In the three subfamilies, the neurochaetae of unit A (upper group) are always inserted above the neuracicula; neurochaetae of unit B (median group) are inserted above, beneath, and below neuracicula; and neurochaetae of units C (lower group) and D (lowest group) are always inserted below the neuracicula in that order. On the contrary, the pattern of insertion of the neurochaetal units in the neuropodia differs among subfamilies; while pelogenins present complex patterns such as marked "C" shaped and "J" shaped patterns of insertion in the neuropodia, sthenelanellins and pholoins present inconspicuous "C" shaped and "J" shaped patterns.
The description and illustrations of the neurochaetae of Sthenelanella species have been heterogenous among studies. Few studies include the characterization of some neurochaetae from middle segments (e.g., Fauvel, 1958); some others have described the neurochaetae briefly by distinguishing the articulate blade from anterior segments and the blunt short blade from middle segments (e.g., Aungtonya & Eibye-Jacobsen, 2013). In such studies, the descriptions were complemented with detailed drawings of the neurochaetae. The proposed classification of neurochaetae by units provides another option to present the descriptions regarding neurochaetae. Using this terminology might help to generate less verbose descriptions, cover all the variety of chaetae and, make descriptions comparable among species (sensu Cruz-Gómez, 2022).
The genus Taylorpholoe was considered monotypic for the past 30 years, yet with the description of T. anabelae sp. nov. this changed. The recognition and description of T. anabelae sp. nov. was possible by considering uncommon features used for sigalionids, but explored in other annelid families (i.e., Sphaerodoridae Malmgren, 1867), such as the distribution, shape and coverture of dorsal papillae. The presence of dorsal papillae was mentioned in previous descriptions of Taylorpholoe specimens (Wolf, 1984;San Martín, Aguirre & Baratech, 1986;Pettibone, 1992); however, in those studies the authors did not evaluate the taxonomical relevance of these dorsal structures. Here, the dorsal papillae were considered taxonomically informative, and they proved their utility to separate the newly described species T. anabelae sp. nov. from the known T. hirsuta. Likewise, the elytra in this genus are taxonomically useful as in any scaled sigalionid; however, while studying the shape of the papillae they should be assessed carefully, since they might suffer a distortion caused by the accumulation of dirt on their cilia (V. Miranda, 2021, personal communication). The marginal papillae found in T. anabelae sp. nov. might be perceived as flask-shaped, similar to the ones illustrated by Taylor (1971: 115, figs. H-I); however, once the elytra are properly clean, the papillae get its actual shape, filiform covered with cilia (Figs. 7V and 7W). As for the examined specimens of Sthenelanella, neurochaetae of specimens of T. anabelae sp. nov. were described using the chaetal unit classification obtaining similar results. In T. anabelae sp. nov. the neurochaetae distribution in middle segments consists of two main patterns: the units A-C forming a continuous "C" shaped pattern surrounding the neuracicular lobe in dorsal to ventral direction, and unit D, inserted in a wide "U" shaped pattern on the ventral side of the parapodia, starting from the anterior side of the parapodia to the posterior side. In contrast, in some genera of Pelogeniinae (i.e., Daypsammolyce Pettibone, 1997, Hartmanipsammolyce Pettibone, 1997, Neopsammolyce Pettibone, 1997, Pelogenia Schmarda, 1861, Psammolyce Kinberg, 1856 the neurochaetal units are presented in different patterns of interrupted fascicles; for instance, in Pelogenia the unit A forms a "J" shaped pattern, while the units B and C form a continuous "C" shaped pattern surrounding the neuracicular lobe, if secondary chaetal units are present they follow the previous "C" shaped pattern, and finally unit D comprehend a wide "U" shaped pattern on the ventral side of the parapodia (Cruz-Gómez, 2022: 4, figs. 1H-1J).
Finally, this study involved the revision of specimens collected from underexplored sites and depths in the Tropical Northwestern Atlantic. Unfortunately, because they were fixed in formalin solution, it was not possible to complement the species descriptions with DNA sequences. However, the lack of molecular information did not impede the determination of the species identities, both in previously described and new species.
Little effort had been made to study these subfamilies of sigalionids in the region; nevertheless, as the studies of these groups increase, the hidden diversity of these small worms is being revealed.

CONCLUSIONS
The subfamilies, Pholoinae, Sthenelanellinae and Pisioninae, are three more-or-less common subfamilies of sigalionids. In the Tropical Northwestern Atlantic, study on these subfamilies has been scarce with only eight species recorded, including questionable records for the region. In this study, three new species were described from this tropical region; the description included detailed images, such as SEM imaging, photographs, and drawings, as well as the use of the unit terminology for neurochaetae recently proposed. The identification keys included herein will help to assist in taxonomical, or ecological studies. In the region as in other oceanic basins, more efforts should take place to increase the knowledge of these sigalionid subfamilies. Along with this work, the result of future surveys focused on these groups of small worms will become an important information input for the study of the phylogeny of the family Sigalionidae.